Photo Gallery

Home > User galleries > Max > Misc lamps and lighting
Return to the thumbnail page FILE 2/122 Return to start See previous file See next file Skip to end
Testing the last SOX-E 26W The electrical characteristics of the Philips SOX-E 26W shown [url=https://trad-lighting.net/gallery/displayimage.php?pid=1163]there[/url] matches its published specs. This is a 27 W lamp indeed (27.5 W to be exact). I measured another lamp made in 2014, and I get a similar value at 0.37 A. So, this is confirmed, Philips did increase the power dissipation of its SOX-E 26W by about 2 Watts when it changed its design in the 2000s. However, the measured rms voltage is quite higher than the published one (85 vs. 69 V), which is probably caused by a different voltage waveshape as I did not use a hybrid SOX-E ballast but a standard SOX leak transformer fed by a variac. Keywords: Lamps

Testing the last SOX-E 26W


The electrical characteristics of the Philips SOX-E 26W shown there matches its published specs. This is a 27 W lamp indeed (27.5 W to be exact). I measured another lamp made in 2014, and I get a similar value at 0.37 A. So, this is confirmed, Philips did increase the power dissipation of its SOX-E 26W by about 2 Watts when it changed its design in the 2000s. However, the measured rms voltage is quite higher than the published one (85 vs. 69 V), which is probably caused by a different voltage waveshape as I did not use a hybrid SOX-E ballast but a standard SOX leak transformer fed by a variac.
DSCF0202.JPG DSCF0265m.jpg DSCF0281m.jpg DSCF0289m.jpg Westinghouse_H33-1-GL21Y_1m.jpg
Lamp/Fixture Information
Manufacturer:Philips
Model Reference:SOX-E 26W
Lamp
Lamp Type:Sodium low pressure
Filament/Radiator Type:Nonthermal discharge in neon, argon, and sodium vapor
Base:BY22d
Shape/Finish:Tubular clear with ITO coating
Electrical
Wattage:27 W
Voltage:69 V
Current:0.37 A
Optical
Lumen Output:3,700 lm
Lumen Efficacy:137.0 lm/W
Colour Temperature:1770 K
Colour Rendering Index:-45 Ra8
Physical/Production
Factory Location:Hamilton, Scotland
Fabrication Date:March 2019
File information
Filename:DSCF0265m.jpg
Album name:Max / Misc lamps and lighting
Keywords:Lamps
Filesize:635 KiB
Date added:06 Apr 2026
Dimensions:1500 x 1000 pixels
Displayed:16 times
DateTime Original:2026:04:06 14:19:17
Exposure Time:1/40 sec
FNumber:f/3.2
File Source:Digital Still Camera
Flash:No Flash
Focal length:18 mm
ISO:160
Model:X-E4
Software:Adobe Photoshop 25.7 (Windows)
White Balance:0
URL:https://trad-lighting.net/gallery/displayimage.php?pid=1191
Favourites:Add to Favourites

Comment 1 to 6 of 6
Page: 1

Tuopeek   [Mon 06 Apr 2026 at 21:35]
Thanks for revisiting this and testing the 26W lamp. If you are using a leak transformer, would it not be a bit higher anyway or are you counteracting this with the Variac? My head get into a mess when thinking about RMS values and measurements of non-sinusoidal wave forms. Smile
Max   [Mon 06 Apr 2026 at 22:00]
You're welcome, Mark. I had fun testing various SOX lamps and seeing how well they can be dimmed down (see the other posts in this series), something I did know expect from lamps with such a finely tuned thermal balance. On the subject of the electrical measurements, the power meter used here provides true RMS values for the voltage and current, so the waveshape is not an issue. I edited the description after your comment in order to clarify that I used a standard 0.6 A SOX leak transformer whose voltage input is adjusted with a variac so as to get an operating rms current matching the nominal one for this lamp, i.e., 0.370 A.

I tested other SOX lamps as well and it seems that the power increase is not limited to the present SOX-E 26W. I also have a SOX-Plus 35W from 2017 which has the same 1.5-cm gap in the ITO coating next to the electrodes and its dissipated power is also higher, 38 W, which corresponds to a 3-W increase. I also found this gap in other lamp types (the SOX-E 18W being the exception given its small size), and although I did not measure them, I'd bet they also have an increased power dissipation.
Sammi   [Mon 06 Apr 2026 at 22:04]
Congratulations on the 1,000th upload.! Love
Max   [Mon 06 Apr 2026 at 22:09]
Is it already? Nice!! Cool
Ria   [Mon 06 Apr 2026 at 22:41]
Fitting that it should be you as well, Max, we are proud to have you as a member here Love
Max   [Tue 07 Apr 2026 at 11:03]
Thank you Ria! It's a pleasure being here Smile

Comment 1 to 6 of 6
Page: 1